Neurotoxic destruction of the dopaminergic cells of the substantia nigra pars compacta of primates and rodents produces useful models of parkinsonism. The 2-[14C] deoxyglucose method is being applied to animals in which unilateral lesions of the substantia nigra pars compacta have been made in order to map the neural circuits involved in the symptoms of parkinsonism and its treatment with dopaminergic agonist drugs. Metabolic studies in rats with anatomically specific lesions of the substantia nigra pars compacta have demonstrated the significance of the loci of the damage to dopaminergic cells along the medial-lateral axis of the nigra in determining the resulting pattern of behavioral effects. Furthermore,the level of functional activity in the substantia nigra pars reticulata has been shown to be the determinant of the directions of turning behavior elicited by the administration of dopaminergic drugs.